Biology: Cell Cycle

Interphase

Growth and Preparation

What does interphase contain?

G0, G1, S, G2

G0

Resting/non-dividing phase

G1

Cell grows

S

DNA and centrosome replication

G2

• Error check; prepares for mitosis, replication of organelles

  • Involves MPF (Mitosis Promoting Factor Protein)

DNA Replication: Prokaryotes

Binary fission for S

DNA Replication: Eukaryotes

S phase

M Phase: Cell Division

Includes Karyokinesis (nuclear division) and Cytokinesis (cytoplasmic division)

Microtubules

Made of tubulin; help move chromosomes

Centrosomes

Organize spindle; contain 2 centrioles (9 X 3 arrangement)

Polar Spindle

Connect centrosomes to opposite poles

Astral Spindle

Anchor centrosomes to cell membrane

Kinetochore Spindle

Attach to chromosomes and pull them apart

Cilia/Flagella

9 + 2 microtubule arrangement (for cell movement)

Cell Regulation

• Surface-to-volume ratio: Low ratio = poor cellular exchange = cell death

• Genome-to-volume ratio: Small nucleus can't support large cell = cell death

G1 Checkpoint

Checks cell size and DNA

G2 Checkpoint

Checks DNA replication accuracy

M Checkpoint

Ensures spindle fibers/microtubules are properly attached to chromosomes

Cyclin + CDK

Promote cell cycle progression

Anchorage dependence

Cells must be attached to divide (promote division)

Density dependence

Cells stop dividing when space is limited

Chromatin

Loose form of DNA

Chromosome

Condensed DNA made from chromatin

Genome

All genetic material (DNA) in a cell

Sister Chromatids

Identical copies of a chromosome

Dyad

A pair of sister chromatids joined by X

Centromere

Region where sister chromatids are joined

Kinetochore

Protein site on centromere where spindle binds

Mitosis

Prophase, Prometaphase, Metaphase, Anaphase (Cleavage furrow), Telophase (Cytokinesis)

Prophase

Chromatin condenses, spindle forms, nuclear envelope breaks down

Prometaphase

Spindle fibers attach to kinetochores

Metaphase

Chromosomes align at the metaphase plate

Anaphase and Cleavage furrow

Sister chromatids pulled apart to opposite sides

Forms using actin and myosin (animal cells)

Telophase and Cytokinesis

Nuclear envelope reforms, chromosomes return to chromatin (no spindle)

Animals: Via cleavage furrow

Plants: Via cell plate and middle lamella

Meiosis

Ploidy Transitions: Diploid (2n) → Haploid (n) → Haploid (n)

Somatic cells

Body cells (undergo mitosis only)

Gametocytes

Germ cells (can undergo meiosis or mitosis)

Gametes

Sex cells (sperm and egg) = 2 autosomal

Meiosis I (Reductional Division)

• Prophase I: Synapsis (pair chromosomes) forms tetrads/bivalents via synaptonemal complex; crossing over at chiasmata

• Metaphase I: Homologous pairs line up; independent assortment adds genetic diversity

• Anaphase I: Homologous chromosomes are pulled apart

• Telophase I: Results in two haploid cells

Meiosis II (Similar to Mitosis)

• Anaphase II: Sister chromatids separate

• Telophase II: Produces four genetically unique haploid gametes